Biomedical subjects

H Kingma

Publications and source records attributed to H Kingma.

At least 37 records · Page 2Linked to original sources

PubMed1995

Interference between saccadic eye and goal-directed hand movements.

The aim of the present study was to investigate the nature of the interference effect when the eye is accompanied by a goal-directed hand movement rather than when the eye moves alone. Latencies of eye and hand movements in response to small and large visual target stimuli were measured while employing dual-task methodology. Experiments 1 and 2 were designed to investigate whether the interference effect is related to a specific temporal bottleneck, i.e. the eye and hand motor systems share limited available processes at a specific point in time. The findings of robust interference effects independent of the temporal organization of eye and hand contradicted this notion. The interference effect was not present in experiment 3, where response preparation and target-localization mechanisms were limited by providing subjects with advance information about target position. Experiment 4 employed randomized target positions again and highly salient stimuli, the latter only limiting target-localization processes. The absence of an interference effect adds weight to the argument that visual spatial attentional mechanisms involved in target localization constitute the locus of the interference. Neurophysiological implications of these findings are discussed.

Adult↗

PubMed1995

Vocal load as measured by the voice accumulator.

Voice disorders related to occupation and work environment are often observed in ENT consultations. Advising these patients requires not only the investigation of their vocal capacities but also knowledge about their vocal load. The patient will name extreme demands as the reason for vocal problems whereas the employer will want to know if the patient is capable of doing the work required of him. For an objective measurement of vocal load, a voice accumulator has been developed. This portable instrument records total speaking time and sound level over a period of several hours. The data can be transferred to a personal computer which analyses voiced time (s) between 60 and 112 dB(A)s. Thus, more precise and objective documentation of vocal demands in some professions can finally be obtained. With these results, it is possible to monitor vocal ability or disability during vocal rehabilitation.

Equipment Design↗

PubMed1995

Real time binocular detection of horizontal vertical and torsional eye movements by an infra red video-eye tracker.

So far it has only been possible to detect horizontal and vertical eye movements during real time; torsional eye movements have to be calculated from video-tape that have been processed several times, and each investigation takes considerable time. We developed a real time binocular infra red video eye tracker for routine clinical examination which allows real time graphical visualization of horizontal, vertical and torsional eye movements with a bandwidth of 12 Hz (25 Hz refresh frequency). Eye movements in three dimensions can now be obtained as easy as has been done before with electronystagmography for the horizontal component. In contrast to previous systems described, we analyze only those parts of the video-frame that are essential for detection of all three eye movements. This results in a huge data-reduction accompanied by a speed-up of analysis. The black pupil centre is detected by an iterative process of analyzing several horizontal and vertical lines of the even video field. The algorithm searches for regions of minimal intensity. Horizontal and vertical eye rotation is then calculated and transformed into Fick's coordinates. Based upon the centre of the pupil four concentric segments are defined in the iris to detect torsion and to enable correction for false rotation. Torsion is detected by cross-correlation of each segment and estimated from the outcome of the correlation coefficients. All transformations are established by predefined stored transformation matrices thus making real time calculations for transformation unnecessary. After corrections for eccentricity and assuming that fixation of the subjects tested was perfect, accuracy appears to be within 0.3 degrees-1.0 degrees for all three dimensions. Linearity after all corrections is within 4-9% within a visual field of 60 x 40 degrees (horizontal x vertical).

Computer Graphics↗

PubMed1995

Visuo-vestibular interaction measurements: an alternative for rotation tests with better discriminatory power?

A vestibular function test is introduced for evaluating visuo-vestibular interaction (VVI), in which a visual target may move asynchronously with a pseudo-randomly oscillating rotatory chair. The results show better discrimination of patients (Meniere's disease, benign paroxysmal positioning vertigo (BPPV), uncompensated peripheral vestibular lesions. whiplash) than do standard tests (torsion swing, velocity step, calorization, smooth pursuit, optokinetics, saccade analysis). For the phase shift, the better performance is shown to stem from improved reproducibility. Signal analysis is done fully automatically, thereby precluding experimenter's bias.

Diagnosis, Differential↗

PubMed1995

Quantitative evaluation of the Vestibular Autorotation Test (VAT) in normal subjects.

UNLABELLED: The Vestibular Autorotation Test (VAT) is a relatively easy method for testing the Vestibulo Ocular Reflex (VOR) at higher frequencies by asking the patient to actively shake his/her head from side to side (jaw) with increasing frequency. In this study we investigated reproducibility and clinical applicability of this method and quantified gain and phase of the VOR in normal subjects. We studied the VOR in 33 subjects over a frequency range from 2 to 6 Hz. Ten subjects were investigated with an angular rate sensor mounted on a headband. In this group the velocity gain tended to decrease at higher frequencies and phase lag increased slightly. In a second experiment (2 subjects) head velocity was detected simultaneously by an angular sensor fixed to a headband and an identical sensor attached to a bite board. It was shown that the gain of the VOR in the first group was underrated and phase shift overrated due to slippage of the headband fixed rate sensor. Therefore in a third experiment, 21 subjects were investigated with the rate sensor attached to a bite board only. In this group VOR gain was close to unity and phase was close to 0 degrees (180 degrees out of phase) from 2 up to 6 Hz. In contrast to other studies, a considerable number of subjects were unable to reach shaking frequencies above 4 Hz. Our results agree with those of recently published reports and disagree with others, both using a headband. This is interpreted as being due to difficulties in sensing head velocity accurately. CONCLUSION: vestibular autorotation is an accurate and reproducible way of testing the high frequency range of the vestibulo-ocular reflex, provided that head velocity is measured by a bite board. Our present work is focused on determining the high frequency characteristics of the VOR in patients suffering from vertigo.

Adult↗

PubMed1994

Reaction time latencies of eye and hand movements in single- and dual-task conditions.

The goal of this study was to investigate whether ocular and hand motor systems operate independently or whether they share processes. Using dual-task methodology, reaction time (RT) latencies of saccadic eye and hand motor responses were measured. In experiment 1, the hand and eye motor systems produced rapid, aimed pointing movements to a visual target, which could occur either to the left or right of a central fixation point. Results showed that RT latencies of the eye response were slower in the dual-task condition than in the single-task condition, whereas the RT latencies of the hand response were virtually the same in both conditions. This interference effect indicated that the ocular and manual motor systems are not operating independently when initiating saccadic eye and goal-directed hand movements. Experiment 2 employed the same experimental paradigm as experiment 1, except for one important modification. Instead of a goal-directed hand movement to the target stimulus, subjects had to make a button-press response with either the index or middle finger of the right hand dependent upon whether the stimulus occurred to the right or left of the control fixation point. The aim of experiment 2 was to investigate the issue whether the observed interference effect in experiment 1 was specific or non-specific (e.g. overhead costs due to coordinating any two responses). The finding that saccadic eye movements and button-press responses in the dual-task condition could be initiated without delay relative to the single-task conditions, supports the specific interference interpretation.

Adult↗

PubMed1994

Functional morbidity of hyperthermic isolated regional perfusion of the extremities.

BACKGROUND: Isolated regional perfusion (IRP) of an extremity is a major operation. The therapeutic value for stage I melanoma is still controversial and is presently being investigated in a prospective, randomized study by the European Organization for Research and Treatment of Cancer. So far there are no reliable data available concerning the morbidity of IRP. Therefore, we performed a prospective, randomized study on this topic. METHODS: In a prospective study, a group of 97 patients with a stage I melanoma localized on an arm or leg were randomized for IRP with melphalan followed by wide excision (WE) and fasciotomy or for WE only. Morbidity was evaluated on the basis of the following parameters: duration of hospitalization, postoperative pain, postoperative performance, and grade of perfusion toxicity. At 12-month follow-up, a physical diagnostic examination was performed to measure the mobility of the joints, and the circumference and volume of the treated and untreated extremities. RESULTS: All the parameters, including the physical diagnostic examination, could be evaluated in 83 of the 97 patients (8 patients died of metastatic disease and 1 patient died of another disease before they could be investigated; 2 patients were in too poor physical condition due to metastases to be examined, and 3 patients were unable to participate for nonmedical reasons). Age and sex distribution were comparable in the various patient groups. Treatment mortality was 0%. There were no complications except for urine retention (one patient) and wound dehiscence (one patient). After IRP + WE of the lower limb, the period of hospitalization was an average of 1.9 days longer (p = 0.01) than for WE on the limb only. This difference was absent for the arm. Naturally after perfusion, there was a significant difference in toxic reactions (edema and pain) between the IRP + WE patients and the WE-only patients. However, at 12-month follow-up, the difference in morbidity between IRP + WE and WE-only patients was no longer present: Morbidity of joints and circumference of the limb were the same. A number of subjective complaints were encountered fairly often after IRP + WE (e.g., pricking sensations or pain during changes in the weather), which can possibly be explained by fibrosis caused by perfusion. These complaints were not quantified further because they did not hinder the patients' functioning. CONCLUSIONS: In a long term, IRP with fasciotomy does not cause any additional morbidity. Immediately after the operation, there was more morbidity as a result of the perfusion, which caused a 2-day-longer period of hospitalization in the patients with lower-limb perfusion compared with those who underwent WE only. These findings are in contrast to those in the literature, in which 25% limitation of motion in the ankle joint after perfusion is mentioned. One explanation may be that we always performed fasciotomy after perfusion to prevent (sub)clinical compression syndrome and avoid late fibrosis.

Adult↗

PubMed1994

Quality of spontaneous general movements in full-term small for gestational age and appropriate for gestational age newborn infants.

Quality of spontaneous movements was studied in 15 healthy full-term appropriate for gestational age (AGA) and in 15 full-term small-for gestational age (SGA) newborn infants. All general movements with a minimal duration of 20 seconds were judged on different aspects of movement quality. From the general movements in each group (AGA: n = 106; SGA: n = 187), dominant patterns were isolated. In the AGA Group 3 dominant patterns of general movements were present. In the SGA Group 5 dominant patterns of general movements were found. Three of those were identical to the movement patterns in the AGA group, the remaining two patterns were unique for the SGA infants. Our results indicate that the three different types of general movements which constitute the major part of the normal repertoire of healthy full-term infants can be used as a reference for normal spontaneous motor behaviour. The two different types of general movements in the SGA infants might be used to discriminate between healthy and neurologically suspect newborn infants. The difference in movement pattern between AGA and SGA infants might be explained by the effect of intrauterine malnutrition on CNS development.

Apgar Score↗

PubMed1993

On the time course and accuracy of spatial localization: basic data and a two-process model.

This article addresses the question how fast and accurate the location of a single stimulus can be perceived. In Experiment 1, we measured localization performance in a task which required subjects to perceive and report the location of a single target stimulus ('*' sign) presented in one square of an imaginary 25 x 19 grid. Two factors were varied: stimulus duration and stimulus eccentricity. Stimulus duration was manipulated by employing a backward masking stimulus. Ten intervals (stimulus onset asynchronies) separated target and masking stimulus: 25, 50, 75, 100, 125, 150, 200, 250, 300, and 350 ms. Stimulus eccentricity was manipulated by presenting the target stimulus at five different distances from the fixation point. The observer localized the target stimulus by moving the cursor from the middle of the grid (the initial fixation point) to the perceived target location by pressing the 'arrow' keys on the keyboard. Localization performance showed to be typically related to stimulus duration. That is, two components could be distinguished: The first component represented an initial steep rise in localization performance during the first 50 ms of stimulus duration; the second component represented a gradual rise in localization performance after 50 ms, reaching maximal performance at about 300 ms. We interpreted these two localization performance functions as reflecting the operation of two systems, namely the attentional system for the initial strong increase and the eye movement system for the subsequent gradual increase. In Experiment 2, we measured saccadic eye response latencies to clarify the role of eye movements in localization performance. It was found that in 98.4% of all trials saccades were executed, and, moreover, that saccadic eye response latency decreased with increasing stimulus duration. In Experiment 3, we compared localization performance in the absence and presence of eye movements and demonstrated that localization performance for stimulus durations up to 50 ms was independent of eye movements. Overall, the present findings were interpreted as evidence in support of a two-process model of localization performance in which a shift of attention is followed by a rapid eye movement toward the target location. In line with a continuous flow conception of visual information processing, our model assumes that location information takes time to develop in the visual system; hence, an observer's localization response may be based on qualitatively different processes operating on qualitatively different kinds of information. In case of short duration stimuli, information conveyed by transient cells is used by the attentional system to shift attention toward the target location; this results in course location information being available.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1993

Postural behaviour of term SGA and AGA newborn infants.

The authors studied the body posture at rest of 15 healthy term infants with birthweights appropriate for gestational age (AGA) and 15 infants who were small for gestational age (SGA). In both groups, there was wide inter-individual variability in postural behaviour. Apart from a preference for a position with all limbs in abduction between 1 and 90 degrees, independent of the degree of flexion or extension and internal/external rotation, no dominant preference posture could be seen for either group. The SGA infants showed a more flexed position of the arms, compared with the AGA group. One of the factors contributing to this difference might be the influence of intra-uterine malnutrition on the development of the central nervous system.

Apgar Score↗

PubMed1992

Inter- and intra-observer agreement in the assessment of the quality of spontaneous movements in the newborn.

The inter- and intra-observer agreement for the assessment of several aspects of the quality of spontaneous movements in newborn infants was analysed by 4 observers. The agreement rates were corrected for chance by the use of kappa statistics, which revealed kappa values ranging from 0.36 to 0.84. The degree of agreement on various items differed. A moderate-to-good agreement was found for the items "onset of movement," "speed," "speed of arms compared to legs," "amplitude of arms compared to legs," "fluency," "variability in arm patterns" and "global judgement of the movement" (kappa values ranging from 0.51 to 0.84). Less agreement occurred in the items "amplitude," "variability in movement pattern" and "variability in leg patterns" (kappa values ranging from 0.36 to 0.40). Even though it is believed that the qualitative assessment of spontaneous motor behaviour is very subjective, our results suggest that several qualitative aspects of infant motor behaviour can be reliably judged. We concluded that the global judgement of the quality of general movements in full-term infants is a reproducible, and therefore reliable, clinical tool for evaluating the function of the central nervous system in the neonatal period.

Humans↗

PubMed1992

State profile in low-risk pre-term infants: a longitudinal study of 7 infants from 32-36 weeks of postmenstrual age.

Spontaneous motor behaviour was longitudinally studied in 7 low-risk preterm infants. The object of this study was to determine whether or not certain recognizable behavioural states exist between 32 and 36 weeks postmenstrual age (PMA), in order to have a well defined recognizable pattern of behaviour during which the preterm infant can be clinically examined. The criteria used to define a behavioural state were: eyes open/closed; crying present/absent; gross body movements present/absent; and respiration regular/irregular. A total of 35 videotapes were made (total time, 99 hours and 25 minutes). For analyzing the data, one second and three-minute windows were used. Our data provide convincing evidence that spontaneous behaviour of preterm infants of 32-36 weeks of PMA can be classified into behavioural states. The variables gross body movements and respiration, are not independent ones. The observed states can be used as a defined clinical condition during which the preterm infants can be clinically examined.

Age Factors↗

PubMed1992

Characterization of the electroglottographic waveform: a primary study to investigate vocal fold functioning.

To objectify the vocal fold functioning we opted for a method of processing the electroglottographic (EGG) signal. This study with 7 normal and 12 pathological voices presents the results of measurements over the chest register as a function of voice intensity and frequency. Reproduction measurements show that at least 5 measurements per intensity/frequency pair are needed to get a reasonable estimation of the EGG parameters. The averaged results over about 20 measurements in the chest register showed differences for some parameters for subjects in the most different categories. To get more consistent results we recommend to improve the measurement protocol and adjust the parameters.

Adolescent↗

PubMed1990

Electrophysiological aspects of the middle ear muscle reflex in the rat: latency, rise time and effect on sound transmission.

The latency, the rise time and the influence of the acoustic reflex on sound transmission were investigated in the adult rat during ketamin anesthesia. This was done by recordings of the cochlear microphonics (CM) and electromyographic (EMG) recordings of the reflex responses of the tensor tympani muscle. The acoustic reflex was elicited by contralateral acoustic stimuli of which the intensity and frequency was varied. Ipsilaterally, the effect on sound transmission was determined by estimating the change in amplitude of the CM's of ipsilateral administered subliminal stimuli. It was shown that both the tensor tympani muscle and the stapedius muscle contribute in the reflex. The latency as well as the rise time of the reflex determined by CM recordings showed to be short (minimal values: 12 and 7 ms respectively). The mean latency of the tensor tympani muscle reflex, measured by EMG, was about 7 ms. The attenuation of 0.25-8 kHz tone bursts upto 115 dB SPL is limited to a mean maximum of 15 dB SPL. The maximal attenuation was shown to occur at 1 kHz. Frequencies above 2 kHz appeared to be the best elicitor of the middle ear muscle reflex.

Animals↗

PubMed1989

The influence of postmenstrual age estimation on the scatter of brainstem auditory evoked potential latencies.

In normal twins the brainstem auditory evoked potential (BAEP) was recorded. The inter-individual variation of the I-V peak latency-interval within the twins appears to be of the same order of magnitude as the variation of the I-V peak latencies generally observed in infants. Consequently we conclude that in low-risk twins the inter-individual variation of the I-V peak latencies of the BAEP is maximally 0.4 msec and cannot be ascribed to a difference in postmenstrual age.

Brain Stem↗

PubMed1989

Posture during head turning in pre-term infants: a longitudinal study of 15 low-risk infants of 32-36 weeks of conceptional age.

As part of a longitudinal study of spontaneous behaviour from 32-36 weeks of conceptional age, body posture was studied during spontaneous head movements in 15 low-risk pre-term infants. At the moment of an active head position in the midline, the most frequently observed posture was a symmetrical one in which the arms were fully flexed and the legs partly extended. With regard to the arm position no clearly developmental trend was noted. With regard to the leg position an increase of the partly flexed position of the limbs related to conceptional age was found. The observed postures during activity in our study showed a cephalocaudal acquisition of flexor tone. A symmetrical posture, when the head is in the midline, may be a sign of normality in pre-term infants.

Gestational Age↗

PubMed1989

Posture of low-risk preterm infants between 32 and 36 weeks postmenstrual age.

The supine posture of 15 low-risk preterm infants was studied to establish whether they have a preferred posture and, if so, whether it changes with age. No over-all preferred posture was found. Almost always one posture was adopted most frequently, but often a great variety of other postures were adopted almost as frequently. There was no correlation between postmenstrual age and preferred posture, the number of different postures, or the duration of longest uninterrupted posture.

Child Development↗

PubMed1988

Influence of head position and head position-change on body posture in pre-term infants (A.T.N.R.).

Although body posture in pre-term infants is generally studied to describe developmental aspects, no consensus exists in literature about the influence of head position and head position change upon body posture in pre-term infants. In a weekly assessed longitudinal study of 15 healthy pre-term infants we extensively observed and analysed the flexion and extension patterns of the limbs in relation to a "spontaneous" head position turning from 32 to 36 weeks of conceptional age. A significant flexion/extension pattern was only observed with respect to the leg: turning of the head induced extension of the chin leg and flexion of the other leg. This pattern persisted during the total 3 hours observation sessions, occurred at every age and in all states, but rapidly disappeared within maximal 20 seconds after the head-turning. No consequent significant pattern was observed with respect to the other limbs or the various other combinations of limb posture changes analysed. An Asymmetric Tonic Neck Reflex was seen after only 3 percent of the head position changes.

Extremities↗